diff --git a/src/client/app/boot.js b/src/client/app/boot.js
index ef828d9637..13abc86ad9 100644
--- a/src/client/app/boot.js
+++ b/src/client/app/boot.js
@@ -30,9 +30,9 @@
 	//#endregion
 
 	// Detect the user language
-	// Note: The default language is English
+	// Note: The default language is Japanese
 	let lang = navigator.language.split('-')[0];
-	if (!/^(en|ja)$/.test(lang)) lang = 'en';
+	if (!/^(en|ja)$/.test(lang)) lang = 'ja';
 	if (localStorage.getItem('lang')) lang = localStorage.getItem('lang');
 	if (ENV != 'production') lang = 'ja';